v0.1.5: Various bug fixes, improved iPython 4.x compatibility, and increased testing.

• Fixed some import issues for iPython 4.x.
• Fixed issues writing a notebook for some versions of iPython and notebook format.
• Fixed some issues reading the notebook for iPython 2.x.
• Add test coverage for the CLI.
• Report statistics on CLI test coverage.
• Perform linting analysis during Travis builds.
• Add more details about the package in the setup script.
• Fixed various formatting issues.